This invention relates generally to the field of rotary dampers, and in particular, to rotary dampers for use in motor vehicle suspensions.
Rotary dampers, as used in vehicle suspensions, typically include a body with a means of fixed attachment and an axle or shaft that is used for rotary attachment. Bodies of vane type dampers have chambers containing fluid and the axle is attached to a rotor with a vane or vanes closely fit into the fluid chambers. When torque is applied to the axle to cause rotation, the vanes apply pressure on the fluid to cause the fluid to flow through orifices or valves. The resistance of the fluid to flow through the orifices or valves causes the rotary damper to resist or damp the motion that is a result of the torque applied to the shaft. This type rotary damper generally includes some air space or a gas accumulator to allow for fluid thermal expansion and fill variation.
Currently, rotary dampers are manufactured with portions of the assembly, such as the valves, orifices, or accumulator, external to the body. This increases the complexity of manufacture and installation. Extra steps are required to install the rotary dampers in the motor vehicle. Parts are exposed, leaving them vulnerable to damage.
In addition, many machining steps are required to meet the high dimensional tolerances required and to form the flow passages directing the fluid through the rotary damper during operation. This increases the cost of manufacture.
Rotary dampers typically provide the same damping regardless of the direction of axle rotation, limiting tuning options. The same torque is applied to the axle whether that is the proper amount of torque needed for that direction.
Accumulators are typically complex mechanical devices, using pistons and seals to provide a gas plenum. This requires fine machining to form a smooth surface piston travel. In addition, the accumulator must be charged with gas before installation, adding another manufacturing step. Seals may fail during operation, allowing the gas to escape the plenum so that the accumulator fails.
Accordingly, it would be desirable to have a rotary damper that overcomes the disadvantages described.
One aspect of the invention provides all valves, orifices and an accumulator to be housed in the body, allowing easy assembly, a compact overall package, and a simple, rugged case.
Another aspect of the invention provides valves configured to provide independent control of damping for each direction of rotation.
Another aspect of the invention provides a design taking advantage of powder metallurgy fabrication, producing precision parts while reducing the machining required and the cost of manufacturing.
Another aspect of the invention provides a closed cell foam accumulator to reduce fabrication and assembly costs and to increase reliability.
The invention provides the foregoing and other features, and the advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention and do not limit the scope of the invention, which is defined by the appended claims and equivalents thereof.